1. Technical Field
The present invention relates to a device for imaging by proximal scanning of a bundle of optical fibers. It also relates to a module for this device and a method implemented by this device.
The field of the invention particularly relates to endoscopy and fibered confocal microscopy.
2. Prior Art
There is a known document WO 06 000 704 A1 that describes a system for fluorescence microscopic imaging by proximal scanning of a bundle of optical fibers.
Such a system comprises lasers that emit excitation beams and an array of dichroic filters, beam splitters, and lenses that guide the excitation beams to scanning means, which alternately inject the excitation beams into a fiber of an image guide from the proximal end of the guide. The guide is made to guide the excitation beams to its distal end placed in contact with or in proximity to a sample. In response to the excitation beams, the sample emits a luminous response flux, collected by the distal end of the guide. The collected flux is guided along the guide, then through the scanning and injection optical system and the array of filters, beam splitters and lenses, to a detector. A filtering hole in front of the detector makes it possible to reject the light that may have been coupled into the fibers of the guide adjacent to those transporting the excitation beams. Thus, only the part of the collected flux that has been guided along the fiber transporting the excitation beams is imaged in the detector.
The optical alignment of the filtering hole relative to the position of the fibers of the guide on the proximal end of the guide is critical because it guarantees the confocality of the system. Such an alignment is complex to achieve, since the typical diameter of the fibers of the guide is a few micrometers. This alignment specifically depends on all of the optical components located between the filtering hole and the image guide.
The technical characteristics of certain optical components of the system strongly depend on the wavelengths of the excitation beams used, particularly the characteristics of the dichroic filters. A first problem with this system is that the laser sources and the dichroic filters are difficult to access in order to change the wavelength of an excitation beam, and it is generally preferable to replace the system entirely.
A second problem with such a system is that it is nearly impossible to replace or reposition an optical component of the system, or to add a new optical component to the system, without having to realign the entire system. In particular, if the system is not realigned, its runs the risk of losing its confocality.
A third problem of such a system is that the proximal scanning approach, while it is efficient in terms of microscopic imaging, is hardly compatible with observation protocols which also require a pre-illumination of the sample, if the duration of this pre-illumination must be longer than the transit time of the laser beam in front of each fiber of the bundle. In such a situation, a non scanning approach would be preferable. Among such protocols, one may think of optical-stimulation, or photo-activation, where a dedicated laser beam is used to activate or silent some specific cells of the tissue to be analyzed.
The object of the present invention is to propose a device that makes it possible to solve all or some of the above-mentioned problems, and a method implemented by such a device.